The goal of the current research proposal is to investigate the effects of core social deficits in autism spectrum disorders (ASD) on the sign language development of deaf children. This will be done by collecting data from 20 autistic deaf children of deaf parents (deaf-of-deaf or DoD) between the ages of 4 and 12 and 45 typically- developing (TD), non-autistic DoD children between the ages of 4 and 12 (15 in each of three age ranges: 4-5, 6-8, and 9-12). Previous research has examined how hearing children with severe autism are able to learn manual signs as an alternative to speech, but no research has systematically examined the signing of deaf autistic children. This study represents a continuation of the PI's research into this population, the first of its kind. This is particularly important due to growing awareness about autism within the Deaf community as well as the steep increase in estimates of the prevalence of autism in recent years (1 in 91 children according to the CDC; 2009). Furthermore, an investigation of the sign language development of deaf children with autism could be particularly illuminating due to the non-linguistic cognitive skills required to learn a sign language such as American Sign Language, or ASL. Several of the core social skills known to be impaired in autism are crucial for sign learning, and thus sign language could show unique effects of autism on cognition that are not observable in speech. These skills include the ability to engage in episodes of joint attention, interpret facial expressions, understand the differing visual perspectives of others and replicate the body movements and stances of others (a complex cognitive process that is involved in discourse (signer/addressee) perspective- taking that we refer to as self-other mapping). The first specific aim is to investigate the effects of autism on sign language acquisition by eliciting targeted structures, including lexical items, agreement verbs, personal pronouns, and classifier constructions. The second aim of the proposed study is to investigate the performance of deaf ASD and TD children on non-linguistic cognitive skills thought to be entailed in self-other mapping, including theory of mind and identification with others, and to analyze possible correlations between performance on the social and linguistic tasks. This research has implications for a clearer understanding of the specific cognitive impairments underlying autistic disorders, and how these impairments affect language acquisition. Since little is known about this population, the knowledge gained will inform the development of diagnostic instruments, educational interventions, and sign language training for deaf children with autism.